Study of Motor Unit Action Potential Conduction Velocity and Firing Rate in Low Force Contractions using Empirical Mode Decomposition

Abstract

Arrays of surface electrodes may be used to record individual motor unit action potential (MUAP) trains from the skin surface. Processing of the later gives access to direct estimation of instantaneous conduction velocity and firing rate of individual MUAPs, which are informative physiological features. However, the estimation of conduction velocity and firing rate may be sensitive to additive noise, which is always present in surface EMG recordings. In this paper, we propose to use the Ensemble Empirical Mode Decomposition (EEMD) to represent individual MU instantaneous conduction velocity and firing rate time-series as a sum of components (intrinsic mode functions) and to omit the components with energy lower than the expected noise level. This approach enables to denoise the conduction velocity and firing rate time-sequencies, extracted from the surface EMG recordings, and to unmask a physiological relationship between them.